Session: 703. Cellular Immunotherapies: Basic and Translational: Poster III
Hematology Disease Topics & Pathways:
Research, Acute Myeloid Malignancies, AML, Biological therapies, Translational Research, Diseases, Therapies, Immunotherapy, Myeloid Malignancies, Biological Processes, Natural Killer (NK) Cell Therapies, Technology and Procedures
SENTI-202 represents an innovative preclinical CAR-NK cell therapy, engineered to exploit a powerful CD33 OR FLT3 NOT EMCN Logic Gate gene circuit, in conjunction with calibrated release IL-15 (crIL15) expression. The CD33 OR FLT3 (OR GATE) activating CAR (aCAR) concurrently targets two AML antigens, thus permitting a broader therapeutic window against AML LSCs (CD33+/-, FLT3+), blasts (CD33+, FLT3+/-), and more specifically, VEN-resistant (VEN-r) AML with a CD33+ monocytic phenotype (Pei, 2020). The NOT EMCN (NOT GATE) inhibitory CAR (iCAR) is a pivotal safeguard, selectively shielding healthy EMCN+ Hematopoietic Stem Cells and Progenitor Cells (HSCs/PCs) from potential off-tumor toxicity. Previously, SENTI-202 exhibited remarkable efficacy in targeting and eliminating CD33 and/or FLT3 expressing AML cell lines, while concurrently safeguarding healthy HSCs/PCs (Garrison et al., ASH, 2022). To further validate the efficacy and broaden the utility of SENTI-202, we conducted assessments on clinically relevant preclinical AML models, along with VEN-r AML patient-derived xenograft (PDX) models. We first assessed the in vitro cytotoxicity and cytokine profiles of CAR-NK cells possessing the SENTI-202 OR Gate and crIL15 against primary R/R AML patient samples (n=11), where we observed significantly higher cytotoxicity compared to unengineered NK-cells (68% vs 19.7%) (p=0.0005, E:T ratio 1:1 for 24h) and increased TNF-a and IFN-g secretion. To further explore CAR-NK cell anti-tumor activity, we screened 10 different PDX samples and discovered that while the median frequency of CD33 and/or FLT3 expression was 99.9% (97.48-100), individual CD33 and FLT3 expression level varied, underscoring AML proteomic heterogeneity and the clinical need for OR Gate approaches. Our initial PDX studies used clinically relevant VEN/HMA-r AML PDX cells (designated as PDX1) obtained from a patient with FLT3-ITD, GATA2, and NRAS mutations, who initially responded to VEN/decitabine treatment but later relapsed. To facilitate in vivo tracking of AML and disease progression, the VEN-r PDX cells were engineered with Akaluc, an exceptionally brighter luciferase compared to conventional luciferase. Following confirmation of AML engraftment in bone marrow through bioluminescence imaging (BLI), the CAR-NK cells, along with unengineered NK-cells, were infused at a dose of 30 million cells per infusion, once a week for three consecutive weeks. The persistence of the CAR-NK cells was detectable for up to 2 weeks after the last infusion. Notably, the infusion of CAR-NK cells resulted in the clearance of bone marrow (BM) disease as evident from BLI one week after the second infusion of CAR-NK cells while unengineered NK-cells failed to clear bone marrow disease. Assessment of CAR-NK cell efficacy in two different AML PDX models is ongoing, along with additional in vitro and in vivo studies that further demonstrate the ability of the SENTI-202 NOT EMCN Logic Gate to significantly protect healthy HSCs from off-tumor toxicity.
In conclusion, CAR-NK cells expressing the SENTI-202 OR Gate and crIL15 demonstrate robust anti-tumor activity against primary AML cells within in vitro cytotoxicity assays and in vivo AML PDX models, including VEN-r AML. These promising preclinical results highlight the potential of SENTI-202 as a targeted and selective therapy for AML, offering a new avenue for overcoming the challenges posed by the heterogeneity of the AML proteomic landscape.
Disclosures: Carter: PinotBio: Research Funding; Revolution Medicines: Research Funding; Syndax: Research Funding; PMV: Research Funding. Andreeff: PMV: Research Funding; Kintor Pharmaceutical: Research Funding.
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